This invention relates in general to weaving and more particularly to a machine for inserting yarn through an array of longitudinal yarns to produce a three-dimensional weave.
Three-dimensional weaves, in contrast to conventional two-dimensional weaves which are most commonly associated with fabrics, have substantial thickness by reason of the fact that the yarns which make up the weave extend in three directions. Comparing the weave with a cartesian coordinate system, some of the yarns extend in the X direction, more of the yarns extend in the Y direction, and still more extend in the Z direction. The individual strands of X and Y yarns may be woven through the parallel strands Z yarns, thus creating the weave. These weaves when impregnated with suitable resins or graphitic materials product extremely light weight and strong composite structures which are useful in the aerospace industry as well as other industries. Moreover, when the yarns are of the ablative variety, such as high modulus carbon or graphite, the composite structure is capable of withstanding extremely high temperatures.
Heretofore, three-dimensional weaves have been produced using procedures requiring a substantial amount of manual labor. As a result, these procedures are extremely tedious and time-consuming. For example, one procedure involves pushing hollow needles through stacked layers of previously woven cloth and inserting yarn of the third direction through these needles. Furthermore, current weaving procedures subject the yarn to substantial shear forces, but ablative yarns have very low shear strength in spite of their high tensile strength, and consequently, the yarns often sever during weaving, thus further delaying the process.
U.S. patent application Ser. No. 666,241, of H. A. Holman, A. W. Kallmeyer, H. C. Paulsen, and W. W. Weaver, filed Mar. 12, 1976, now U.S. Pat. No. 4,019,540, discloses a Loom for Producing Three Dimensional Weaves, but this application is concerned primarily with producing shed openings in an array of longitudinal yarns so that cross yarns may be inserted through the shed openings in two directions to create a three-dimensional weave. The loom is ideally suited for use with ablative yarns since it does not impose excessive shear stresses on the yarns. However, the patent does not show an apparatus for automatically inserting yarn through the shed openings in the longitudinal yarns.